Edge-lit technology incorporates a light source coupled to a light-guiding member that utilizes total internal reflection (TIR) to direct light from the light source to the desired application space. Various forms of this technology have been introduced in applications that include signs, flat-screen televisions, laptops, mobile phones, luminaires, and other displays. Fluorescent and LED light sources are common for these applications because they can be made to fit in confined fixtures. A slender light source combined with a thin light-guiding member, or lightguide, allows for displays to maintain very low profiles, which is a desirable aesthetic and physical feature for many of the aforementioned applications. In particular, the rise of the LED as a cost-effective light source in recent years has brought opportunities for sleek luminaires which are both energy efficient and long lasting to illuminate commercial and retail space.
A common type of edge-lit luminaire is the recessed troffer, which is a luminaire that is usually intended for drop ceilings in commercial and retail space. These luminaires are only visible from below, so it is not especially critical what the luminaire looks like on the sides or back since it is covered by the ceiling. The luminaire can therefore be fastened together in any number of means which may otherwise be aesthetically unappealing when compared with a suspended or surface-mounted luminaire. Additionally, these luminaires have back panels that span the area of the luminaire, which is typically on the order of 2-8 square feet. The large area offers an advantage in designing for mechanical stability and dissipation of heat generated by the light source(s). A disadvantage of the edge-lit recessed troffer is the restrictive design space in which to direct light from the source to the desired application space. This design space is in part governed by the height of the ceiling and the dimensions of the ceiling grid. These parameters must often be accounted for in the luminaire design prior to commercialization because the luminaire's intended light distribution is not necessarily adjustable for all ceiling heights once it is manufactured. By contrast, suspended and surface-mounted luminaires have more flexibility in mounting location because the end-user can mount the luminaire to any desired height. This flexibility of mounting location brings more scrutiny to the aesthetic of the suspended or surface-mounted luminaire since it is visible from most or all angles and not hidden in a ceiling.
Another application of the edge-lit luminaire is in signage. A familiar example is the edge-lit “EXIT” sign, which features a surface-mounted housing, a light source, and a lightguide. These signs serve an essential safety function and are not designed for large area illumination as recessed troffers and other edge-lit luminaires often are. Additionally, they are not heavily scrutinized for all aesthetic qualities, particularly with respect to bright spots created by LED light sources. Luminaires which are visible from nearly all angles, e.g. suspended or wall-mounted luminaires, are desired to have a uniform luminance while illuminating a large area with a specified light level.